Volume 13 (2007): Issue 1 (January 2007)

This paper presents a simple method of determining the effective attenuation coefficient from steady-state diffuse reflectance measurements.

Ventilation of the lungs involves the exchange of gases during inhalation and exhalation causing the movement of respiratory gases between alveolars and the atmosphere as a result of a pressure drop between alveolars and the atmosphere. During artificial ventilation what is most important is to keep specific mechanical parameters of the lungs such as total compliance of the respiratory system C_p (consisting of the lung and the thorax compliances) and the airway resistance R_p when the patient is ventilated. Therefore, as the main goal of this work and as the first step to use our earlier method of added lung compliance in clinical practice was: 1) to carry out computer simulations to compare the application of this method during different expiratory phases, and 2) to compare this method with the standard method for its accuracy.

The primary tests of the added-compliance method of the main lung parameters measurement have been made using the RC mechanical model of the lungs.

The paper presents the use of the Monte Carlo method to determine the optical parameters of tissue from steady-state diffuse reflectance measurements.

The objective of this paper was to improve the well established in clinical practice Marmarou model for intracranial volume-pressure compensation by adding the pulsatile components. It was demonstrated that complicated pulsation and growth in intracranial pressure during infusion test could be successfully modeled by the relatively simple analytical expression derived in this paper. The CSF dynamics were tested in 25 patients with clinical symptoms of hydrocephalus. Basing on the frequency spectrum of the patient's baseline pressure and identified parameters of CSF dynamic, for each patient an "ideal" infusion test curve free from artefacts and slow waves was simulated. The degree of correlation between simulated and real curves obtained from clinical observations gave insight into the adequacy of assumptions of Marmarou model. The proposed method of infusion tests analysis designates more exactly the value of the reference pressure, which is usually treated as a secondary and of uncertain significance. The properly identified value of the reference pressure decides on the degree of pulsation amplitude growth during IT, as well as on the value of elastance coefficient. The artificially generated tests with various pulsation components were also applied to examine the correctness of the used algorithm of identification of the original Marmarou model parameters.